What Brannon says is great - we have an outlet before our DI cannister too.
DI water literally is deionized water - it is in its purest form with ions of any elements stripped out of it. Before it touches air its pH is neutral at 7.0 .. When exposed to air DI water is aggressive and will leach Co2 out of the air and drop the pH a little.
Aggressive water wants to absorb everything and anything it can - it can affect hard metals as well as other things. Drinking in very small portions (sometimes I have to taste test my buckets to make sure I'm topping off with fresh instead of salt water, yeah I could just mark them with a Sharpe) shouldn't do any harm.
However if you begin to consume very large amounts of DI water in a short amount of time, it will leach from your body as well as you digest it. It can cause an electrolyte imbalance and in more sensative people, headaches.
It should be safe to mix for say, coffe or tea or what not because you are then no longer ingesting deionized water, as it will have dissolved whatever you put into the water.